User Manual

UHF Analog Driver/ Transm it ter Chapter 4, Circuit Descript ions
LX Series, Rev. 0 4- 23
4 .5 .5 ( A4 ) Coupler Board Assem bly
( 1 3 0 1 9 4 9 ; Appe ndix B)
The UHF coupler board assem bly
provides a forward and reflected power
samples of the output to (A5) the
am plifier control board where it connects
to the input of the overdrive- protection
circuit.
The RF input to the UHF coupler
assem bly, from the 250 Watt UHF
am plifier m odule, connects to SMA jack
J1. The RF is connected by a stripline
track to the SMA type connector RF
Output jack J2. A hybrid- coupler circuit
picks off a power sam ple that is
connected to SMA type connector jack J3
as the forward power sample. Another
power sam ple is taken from the coupler
circuit that is connected to SMA type
connector jack J6 as the reflected power
sample. Two 50Ù terminations, used as
dissipation loads, connect to the reject
and reflected ports, J5 and J4, of the
coupler.
4 .5 .6 ( A5 ) Am plifier Control Board
( 1 3 0 1 9 6 2 ; Appe ndix B)
The amplifier control board provides LED
fault and enable indications on the front
panel of the module and also perform s
the following functions: overdrive
cutback, when the drive level reaches the
am ount needed to attain 110% output
power; and overtemperature, VSWR, and
overdrive faults. The board also provides
connections to the LCD Display for
monitoring the % Reflected Power, %
Output Power, and the power supply
voltage.
Page 1
U4, located upper center of page, is an in
circuit microcontroller. The controller is
operated at the frequency of 3.6864 MHz
using crystal Y1. Program m ing of this
device is perform ed through the serial
program m ing port J2. U4 selects the
desired analog channel of U1 through the
settings of PA0- PA3. The outputs of Port
A mu st be set and not changed during an
analog input read of channels PA5- PA7.
PA4 of U4 is a processor operating LED
that m onitors the + / - 12 VDC. PA5 is used
to m onitor the + 12VDC supply to the
board. PA6 is the selected channel of
analog switch U1. PA7 is connected to a
via, V10, for future access.
U6 is a serial to RS- 485 driver I C. U7 is a
watchdog I C used to hold the
microprocessor in reset, if the supply
voltage is less than 4.21 VDC. U7
mom entarily resets the microcontroller if
Pin 6 (!ST) is not clocked every second. A
manual reset switch is provided but should
not be needed.
Upper left corner U3 is used to determine
where the amplifier control board is
located. The eight inputs come from the
main amp connector and are used to set
the SCADA address of the controller. Pull-
up resistors set a default condition of logic
high.
U5 below U3 is used for getting digital
input information of the board. Page two
has several m onitoring circuits that provide
information on the amplifier’s status. Many
of these circuits autom atically shut down
the amplifier if a specific fault occurs.
U8 below U5 is used to control four board
mounted status LEDs. A FET is turned On
to shunt current away from the LED to turn
it Off. U9 below U8 is used to enable
different features within the software.
Actual use is to be determined.
Page 2
In the lower right corner are voltage
regulator circuits. U22 should allow for
0.14 am ps of power using its 92 C/ W
rating if Ta = 60° C m ax and Tj = 125°C
max 0.26 amps can be obtained from U22
if the m ounting pad is 0.5 square inches.
The controller will not need this much
current.
U23 and U24 are low drop out + 5 VDC,
voltage regulators with a tolerance greater